1. Field of the Invention
The invention relates in general to a distributed computing system, particularly to a system that allows dynamic allocation of computing tasks.
2. Description of Related Art
In the 1990's, the “Internet,” a connection system that links computers worldwide in a network, has grown from mainly an academic usage to a widespread medium for the transfer of information. The Internet has been termed the so called “information superhighway.” As more and more computers are connected via the Internet or a network such as an intranet or wide-area-network (WAN), information is not the only resource that is shared within a network of computers. A network will also be utilized in distributing computing tasks such as mathematical calculations, word processing, graphic design, and etc. Since tasks and files are distributed among various computers, a system is required to balance the computing tasks among a plurality of servers.
Presently, various load-balancing methods have been developed to address the problem of overloading computing tasks on one particular server. For example, for a web site having several servers but operating under a single uniform resource locator (“URL”), a domain name server (“DNS”) will send information requests for a specific URL to specific IP addresses corresponding to the servers. In a round-robin DNS, load balancing is achieved by routing requests to these servers in sequential rotation based on their IP addresses. However, since the DNS just routes requests sequentially, this method does not consider the load of the servers and a request can be routed to a server that has failed or does not have the load to perform the request.
Another method is to dedicate a hardware device such as proxy gateways or an IP redirector to perform load balancing. The proxy gateway receives all the requests, queries the servers to determine their respective loads, and then distribute the requests accordingly. Responses from the servers are routed back to the network through the proxy gateway. Unlike the DNS-based method, all requests resolve to the IP address of the proxy server, which avoids the problem of failed servers. However, dedicated load balancers also have a drawback of relying on “old information” as the proxy gateway can only query the servers so often without creating undesirable overhead on the network. Also, these hardware devices only route tasks based on requests and do not consider other important aspects of a computing tasks. For example, in an Application Service Provider (ASP) model, client attributes, such as memory space and computing power, need to be matched up with the fulfillment server attributes, such as data format and size of the output. If the computing task is to produce a video image by the fulfillment server, the output of the server needs to be in a specific format that the client can visualize. Thus, there is a need for a load-balancer that can track the differing capabilities of various servers in fulfilling a client's need.
U.S. Pat. No. 6,128,279, to O'Neil et al., solves the old information problem by teaching a peer-to-peer load balancing method in which a server in a plurality of servers determines whether it can serve the request or whether it should direct the request to another server. Although the information is real-time, the redirecting of the request is accomplished by the server itself, which creates a problem with scalability. As server number increases, each server needs to track the load of other servers and thus, diverts the server's computing power from its main task of fulfilling requests. Also, like the previous methods mentioned, the peer-to-peer load balancing tracks only load and neglects various attributes of a client, a server, and a request.
Therefore, it is advantageous to have a scalable system to distribute computing tasks that considers attributes of the client, the server, and the request.